Method of energy control in printing with transfer ribbon and direct thermo material in thermo-printers

ABSTRACT

The invention relates to a method for controlling the amount of energy from a printer head in a thermo-printer. The appropriate amount of energy for obtaining the best possible print quality with a certain printing material is controlled through calculating the amount of energy required as a function of the printing speed of the printer, over the full range of printer speed, and of the characteristic printing material data. The printing speed is continuously variable within the complete printing speed range of the printer. Characteristic data for the printing material are classified for magnitude and may be given as an offset relative to a reference material, or as absolute values.

BACKGROUND OF THE INVENTION

The transfer of ink from a transfer ribbon to the receiving material,e.g. a paper label, and the colouring of direct thermo material iscontrolled by variable amounts of thermal energy. Depending on howsensitive the transfer ribbon or the direct thermo material is for theseamounts of energy, and on what printing speed is used, more or lessenergy is required to obtain the desired print quality and result in theform of a printed image.

SUMMARY OF THE INVENTION

The object of the present invention is to achieve the highest possibleprint quality on an arbitrary printing material by utilizing anappropriate amount of energy at an optional printing speed.

This object is accomplished by the method according to the followingdescription.

DESCRIPTION OF THE DRAWINGS

The FIGURE is a block diagram of a method of the invention.

DETAILED DESCRIPTION

The present invention relates to a method for controlling the amount ofenergy that is emitted from the thermo head of a thermo-printer in orderto obtain the desired ink transfer or colouring. The amount of energycan be described as a function of printing speed and characteristicprinting material data according to the following formula or controlalgorithm:

E=f(printing speed, characteristic printing material data) for example

E=C+(F×((300−v)/(2×v))),

where E is the amount of energy, v is the printing speed and C and F area Constant and a Factor, respectively, characteristic of the printingmaterial. The maximum printing speed for which the function is valid is300 mm/s in this example, but the speed can be increased bymodifications to the function. C as well as F may be multiplied byfurther factors in order to give the curve a different slope within thespeed interval in question. Furthermore, the amount of energy depends onthe mechanical pressure applied by the thermo head on the transferribbon/receiving material or the direct thermo material, but thepressure may be considered to be the same for the same type of printers.Other properties affecting the ink transfer or colouring may be thesurface chemistry etc. of the materials, but such properties may beregarded as being the same for the same type of materials.

The energy of each individual dot in the thermo head can furthermore bedescribed by how this dot has been used in the past, how adjacent dotsare used and how the dots in front will be used, and by the resistanceand the temperature of the thermo head. However, this historicaldifference in the energy amount follows a constant reciprocal functionthat is independent of the printing speed.

An appropriate formula (control algorithm) is stored in the printersoftware, and this algorithm is subsequently used for calculating theappropriate energy amount for each combination of transferribbon/receiving material or direct thermo material, and printing speed.

When determining the appropriate amount of energy for several transferribbons onto one and the same receiving material, it has been found thatthe offset energy (positive or negative) required when printing on adifferent receiving material will be the same for all transfer ribbonsor classes of transfer ribbons (wax, wax/resin, resin). Similarly, thesame formula can be used for direct thermo materials with similarthermal sensitivity.

The criteria used when determining the appropriate amount of energy maye.g. be the print's optical density, bar code quality according toANSI/CEN, or widening of the bars of a bar code.

The advantages of the method of the present invention are as follows:

One printer setting will work over the entire speed range of theprinter. The physical limits of the materials regarding printing speedmust however be considered.

Simple switching between different combinations of transferribbons/receiving materials or direct thermo materials.

Possibilities of adjusting the print quality to the requirements of theuser.

Possibilities for systematic marking of transfer ribbons, receivingmaterials and label materials that will allow easy and simple optimumsetting of the printer, for the materials in question, by the user.Furthermore, it will be simple to widen the assortment of transferribbons and materials with new qualities, with information about theoptimum printer setting.

What is claimed is:
 1. Method for controlling a printer head in athermo-printer comprising the steps of: identifying a print material,print ribbon and printing speed; calculating an amount of energyrequired by the print head according to: E=C×(F×((Vmax−V)/(2×V))) where: E=Energy level required C=a constant, characteristic of theprinting material F=a factor, characteristic of the printing materialVmax=the maximum printing speed of the printer V=the current printingspeed of the printer; energizing the print head with the calculatedamount of energy required.
 2. The method of claim 1 further including afactor representing a level of mechanical pressure between the printhead and the print material in the calculation of the amount of energyrequired.
 3. The method of claim 1 further including a constantrepresenting recent activation of individual dots of the print headdesired to be activated in the calculation of the amount of energyrequired.
 4. The method of claim 3 further including a constantrepresenting recent activation of individual dots adjacent to individualdots of the print head desired to be activated in the calculation of theamount of energy required.